This invention relates generally to condition-responsive switches and, more particularly, to a switch for controlling more than one circuit in response to a specified temperature reference point.
Switches that are responsive to temperature changes, commonly known as thermostats or cold controls, are widely used in refrigeration systems, and typically regulate the switching cycle of a compressor in response to the temperature of the air contained at a remote location. When the temperature exceeds a certain xe2x80x9cturn-onxe2x80x9d point, the switch contacts are closed and the compressor is switched on to cool the air. When the temperature drops below a certain xe2x80x9cturn-offxe2x80x9d point, the switch contacts are opened and the compressor is switched off. Thus, the thermostat opens and closes a main electrical circuit in response to temperature changes at a specified location.
Sometimes, however, it is desirable to also control an auxiliary circuit in response to changes in temperature at the same location that stimulates the main circuit. Thus, extreme temperature conditions, or fault conditions in the main circuit, may be corrected by or identified by auxiliary elements connected to the auxiliary circuit.
Accordingly, it would be desirable to provide a condition responsive switch capable of providing temperature control of both a main circuit and an auxiliary circuit.
In an exemplary embodiment of the invention, a condition responsive electric switch includes a housing, an actuator arm, a movable electrical contact, and an adjustable electrical contact for completing an auxiliary circuit. The actuator arm is mounted within the housing for pivotal movement that moves the movable contact and opens and closes the movable and adjustable electrical contacts to complete or break an auxiliary circuit through the switch in response to environmental conditions outside of the housing, such as the temperature of a specified reference point.
When the reference temperature falls, refrigerant inside a bellows and in fluid communication with the temperature reference point contracts and moves the actuator arm, which causes the movable contact to engage the adjustable contact and complete an auxiliary circuit. As the temperature of the reference point rises, the refrigerant expands in the bellows and causes the actuator arm to move and disengage the movable contact from the adjustable contact. Thus, the auxiliary circuit can be used to avoid excessively cold temperatures at the temperature reference point, by, for example, switching on a heating element through the auxiliary circuit.
The position of the adjustable contact relative to the movable contact is adjustable to calibrate the sensitivity of the auxiliary circuit to movement of the actuator arm. Thus, the auxiliary contact may be moved closer to or farther away from the movable contact to vary the required temperature change, or differential in the reference point temperature that cause the movable contact and the auxiliary contact to engage, thereby closing the auxiliary circuit. The smaller the separation of the movable contact and the auxiliary contact, the smaller the temperature differential at the reference point that will close the contacts.